One problem faced by users of telecommunication systems is that conversations may suffer from unnaturally high end-to-end delay, which we refer to here as latency. When the latency is high enough, it can disrupt normal conversational behavior, for example by causing speakers at the respective ends of the conversation to talk over one another and thus forcing them to expressly negotiate whose turn it is to speak. In view of this problem, users of citizens band radio long ago adopted the convention of saying “over” at the end of each conversational turn. However, such a convention would be unacceptable for high-quality communications.
User dissatisfaction may be aggravated by a common misunderstanding: the problem is often misattributed to poor etiquette, while the role of latency goes unrecognized.
In the case of video reception, the problem may also be misattributed to incompetent operators or faulty equipment at the transmission end. This may be especially troublesome when news correspondents, for example, are reporting from a great distance over a satellite link, which will typically have relatively large delays.
In the past, it has been common practice to simply rely on adaptation by the users of high-latency communications. Purely by listening (which provides auditory feedback), users are generally able to adapt from a range of zero to 150 msec of delay, which is perceived as “normal”, to roughly 400 msec of delay. Simple reliance on user adaptation has generally been satisfactory for casual conversations over free-of-charge systems, where user expectations are relatively low. However, it has not, in general, been highly satisfactory to users of regular mobile calls, particularly when attempting to engage in fast-moving dialogue.